[Cryptography] Signal Security / Secure Chat Metadata Traffic Analysis Generally

[arxlight]

I have always been of the mind that quite a bit of probative information 
regarding the actual security of various secure chat applications, their 
implementation, and the actual use habits of their users as these impact 
practical, realized security, can be found in the sorts of evidentiary 
material related to these applications that eventually finds its way 
into the court system. In the case of high-profile criminal prosecutions 
(particularly of the U.S. variety) the exhibits that result are the 
fruits of a very robust threat model. I am perhaps dating myself to 
observe that this has been a bit of a tradition on the list, though an 
old one, by remembering some discussion in here, not entirely 
tongue-in-cheek, about the utility of using "Ken Starr units" as a 
threat model measure.

When I had more time on my hands I made it a habit to peruse complaints 
and exhibits involving the larger international drug smuggling 
prosecutions in this vein.

So, it is difficult not to think that there is quite a bit to suss out 
of "Government Exhibit 1083 - 'Signal Groups Samuel Bankman-Fried 
Participated in from 2020 to 2022,'" filed with the United States 
District Court for the Southern District of New York in the matter of 
The United States of America v. Samuel Bankman-Fried (a/k/a "SBF"). Not 
finding any restrictions on attachments in the list rules and since the 
.pdf file is small, I attach it here.

I don't want to lead too severely any discussion that might follow here 
but I found it rather interesting that over the course of a few days in 
November of 2022, Signal's Auto Deletion feature was, according to the 
document, turned off on dozens of the 325 listed groups. Perhaps some 
panicked compliance official persuaded the FTX team (or SBF himself?) 
that this feature was legally dangerous? As far as I can tell, Joe 
Bankman was the only actual lawyer listed as a participant in these 
various groups. Mr. Bankman-Fried was arrested in the Bahamas December 
12, 2022. Perhaps he had criminal defense counsel a month earlier who 
warned about the hazards of spoliation?

Of course, all the government needed (I think?) to recover this chat 
information was SBF's unlocked (or locked, if they had the capacity to 
break in) phone, but it will be interesting to see exactly how the 
material is developed and if more material comes to light.

In the interim, I'm quite interested to learn what the list gleans from 
this document.
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